Mechanism for the tiltable seat of a chair

ABSTRACT

A pivot mechanism for a chair seat in which a torsion bar is fastened at its ends within a tube and to the underside of a seat. A support member fastens the tube for relative rotation about its own axis to a seat base. The tube has a transverse opening therein through which an arm rigidly attached to said torsion bar extends. The arm is positionable with respect to an abutment on the support member by means of a manually operable torque varying mechanism.

United States Patent [15] 3,669,399 Wager 51 June 13, 1972 [54] MECHANISM FOR THE TILTABLE [56] References Cited EAT F A CHAIR S 0 UNITED STATES PATENTS t W N th' [72] 3: 5 2,051,043 8/1936 Herold ..248/374 g 2,424,753 7/1947 Herold 297/304 [7 3| Assigncc: Universal ()il Products Company, Des 2,718,257 9/1955 Lie 248/373 lluincs, 111. 2,971,569 2/1961 Parrott et 31.. ..248/3 73 3,59 54 1971 W'l' 4 22 l ilcd: 011.5, I970 8 8/ 2 8/373 [2| Appl. No.1 77,998 Primary Examiner-Marion Parsons, Jr.

Attorney-James R. Hoatson, Jr. and Philip T. Liggett [30] Foreign Application Priority Data 57 S C Oct. 4, 1969 Great Britain ..48865/69 A pivot mechanism f a chair seat in which a torsion bar is fastened at its ends within' a tube and to the underside of a [52] US. Cl ..248/373 seat A upport member fastens the tube for relative rotation 1111- C1 "A476 3/023 about its own axis to a seat base. The tube has a transverse [58] Field f S ar h 1 opening therein through which an arm rigidly attached to said 7/ 267/ 1 57 torsion bar extends. The arm is positionable with respect to an abutment on the support member by means of a manually operable torque varying mechanism.

6 Claims, 3 Drawing Figures I i E 91 i 5 ii, i i i v a s :l H H PATENTEDJUH 13 I972 SHEET 10F 2 Figure 2 Figi/re 1 inul'ln ililltivv'nlllilllulllllllnuln IN VE/V 7'0 R John Stewart Wager wfwe A T TORNEYS PATENTEnJummn 8,669,399

SHEETZUFZ Figure 3 1 "1 l I i l/ N VENTOR:

Jo/m Stewarf Wager A 7' TORNEYS MECHANISM FOR THE TILTABLE SEAT OF A CHAIR This invention relates to a pivot mechanism for the tiltable seat of a chair or like seating device.

It is conventional in some forms of ofiice chair to provide a seat which not only swivels about a vertical axis but can also be tilted backwardly about a horizontal axis against the force of a return spring. This return spring can be a torsion bar. However, a requirement exists for a simple and economic pivot mechanism to permit such tilting movement.

According to the present invention there is provided a pivot mechanism, for the tiltable seat of a chair, comprising a tube through which a torsion bar extends, the ends of the bar being rigidly secured to the adjacent ends of the tube, means for rigidly securing the tube to the underside of the seat of a chair, a support member in whichthe central portion of the tube is journaled for rotation about the axis of the tube, the support member having coupling means for mounting the member on the base of a chair, the tube having an opening in said central portion, an arm rigidly secured to the torsion bar extending outwards through said opening, and a manually operable mechanism for moving the outer end of the arm relative to the support member to vary the torque in the bar.

The present invention also provides a pivot mechanism for the tiltable seat of a chair, comprising parallel-spaced elongate members for attachment to the seat, a tube extending between and rigidly secured to said elongate members, a torsion bar disposed within the tube and rigidly secured at its ends to the tube or elongate members, a support member disposed adjacent the central portion of the tube and having spaced bearings in which the tube is journaled, and coupling means for securing the support member to a base of the chair, said tube being open between said bearings, and an arm rigidly secured to the torsion bar and extending away from the bar through the opening, the outer end of the arm being movable, relative to an abutment on the support member, by means of a manually operable torque-varying mechanism.

One embodiment of the present invention is illustrated in the accompanying drawings in which:

FIG. 1 is a section in a horizontal plane through a pivot mechanism;

FIG. 2 is a section on the line 2-2 of FIG. 1, shown in elevation; and

FIG. 3 is a section on the line 3-3 of FIG. 1.

The chair to which the pivot mechanism of the present invention is applicable will normally comprise a seat part having a rigid panel on the upper face of which a seat cushion is mounted, and a base part in the form of a floor support and a pedestal or column upstanding from the floor support on which the rigid panel of the seat part is mounted through the pivot mechanism. v

The pivot mechanism, as shown in the drawings, comprises a horizontal pivot tube 10 rigidly connected at its opposite ends to elongate angle members 11 which are parallel to each other and perpendicular to the torsion bar 17. These angle members are screwed to the underside of the seat panel. At the mid-length position of the tube, the tube extends through a central support member 12 in the form of a casting which has a pair of apertured bosses spaced apart and forming bearings 13 for the tube. The casting extends laterally of the tube in the form of an abutment plate 14 which, in the normal position of the seat, rests against the underside of the seat panel. The casting also extends laterally of the tube, on the side thereof opposite to the plate, in the form of a coupling arm 15 which is spaced from the underside of the seat panel and includes a vertically-extending thick walled sleeve 16 of which the inner surface tapers slightly in the upward direction and is designed for the reception therein of the tapered upper end of a vertical seat column. I

Extending coaxially throughout the length of the pivot tube is the rectangular-section torsion bar 17 which at its opposite ends is rigidly connected to the tube and to the seat mounting angle members 11 by locking members each in the form of an end cap or plug 18 having a central opening for reception of the end of the torsion bar and a series of peripheral projections (not shown) for engagement in corresponding recesses in the seat mounting angle members.

The pivot tube 10 has part of its wall cut away between the two bearings of the central casting to provide an opening 19 which exposes the torsion bar extending through the tube, and this portion of the torsion bar is rigidly connected to a torquebearing arm 20 which extends outwardly through the opening of the tube. The peripheral extent of the opening is sufiicient to allow angular movement of the torque-bearing arm relative to the tube equal to the maximum tilting movement of the seat. The arm 20 has a transversely-extending screw-threaded hole 21 near its outer end in which engages a torque-varying screw 22, and one end of the screw bears against the plate 14 of the central casting whereas the other end supports a handle 23.

A sheet metal stop bracket 24 is welded to the pivot tube 10 at positions equidistant from its center and is located between the seat panel and the coupling 15 to limit the backward tilting movement of the seat. Moreover the bracket is bent around, at its center to engage under the coupling 15 and overcome the danger of the seat occupant inserting part of his hand between relatively pivoting parts of the mechanism.

In operation of the pivot mechanism, the backward tilting movement of the seat, resulting from backward movementiof the seat occupant, causes the seat mounting angle members 11 and the tube 10 welded therebetween to pivot rearwardly, and thus the outerends of the torsion bar are rotated in the same direction. The central portion of the torsion bar however is secured to the torque-bearing arm 20 which, through the torque-varying screw 22, presses on the abutment plate which forms part of the support member 12, and hence part of the base of the seat. Thus the center of the torsion bar is held against pivotal movement in a vertical plane relative to the seat column and, as the tilting movement of the seat increases, so the biasing return force, or torque, in the torsion bar increasingly opposes further backward tilting movement. A limit stop is formed by the stop bracket 24 which is engaged in the backward tilting direction by the upper side of the coupling 15, whereas forward tilting movement is limited by engagement of the plate 14 of the central casting against the underside of the seat panel. The force of the return spring formed by the tension bar can be varied by rotation of the torque-varying screw 22.

In assembling the pivot mechanism, the central casting is positioned on the pivot tube and the stop bracket is located on the tube and welded in position. Bearing bushes are fitted on the tube and pressed into the bosses of the casting. The torque-varying arm is positioned in the opening of the pivot tube, and the screw handle 23 is fitted to the outer end of the torque-bearing arm. The torsion bar is fed through the pivot tube and torque-bearing arm, and the seat mounting angle members and end caps are fitted on to the torsion bar and angle members. The torsion bar is pre-loaded by rotating the seat mounting angle members and end caps relative to the pivot tube to a predetermined position, and then the angle members and end caps are welded to the pivot tube.

The torsion bar can comprise either a single element of rectangular or other non-circular section or two or more coextensive elements of any desired section.

I claim as my invention:

1. A pivot mechanism, for the tiltable seat of a chair, comprising a torsion bar, a tube through which said torsion bar extends, the ends of the bar being rigidly secured to the adjacent ends of the tube, means for rigidly securing the tube to the underside of the seat of a chair, a support member in which the central portion of the tube is journaled for rotation about the axis of the tube, the support member having coupling means for mounting the support member on the base of a chair, the

tube havingan opening in said central portion, an arm rigidly secured to the torsion bar extendingoutwards through said opening, and a manually operable mechanism for moving the outer end of the arm relative to the support member'to vary the torque in the bar.

' member has bearings for the tube disposed on opposite sides of said opening in the tube.

3. A pivot mechanism according to claim 2 wherein the base of said chair has an upward extending pedestal, and the coupling means of the support member has a sleeve formed with a tapered seating for the reception therein of a tapered upper end of said pedestal.

4. A pivot mechanism according to claim 2 having a stop member rigidly secured to the tube for engagement with the support member to limit the pivotal movement of the seat relative to the base of the chair in one direction.

5. A pivot mechanism for the tiltable seat of a chair, comprising parallel-spaced elongate members for attachment to the seat, a tube extending between andrigidly secured to said elongate members, a torsion bar disposed within the tube and rigidly secured at its ends to the tube and elongate members, a support member disposed adjacent the central portion of the tube and having spaced bearings in whichthe tube is journaled, and coupling means'for securing the support member to a base of the chair, said tube being open between said bearings, and an arm rigidly secured to the torsion bar and extending away from the bar through the opening, the outer end of the arm being movable, relative to an abutment on the support member, by means of a manually operable torque-varying mechanism.

6. A pivot mechanism according to claim 5 wherein the support member is a casting in which said sleeve, bosses forming said bearings, and said abutment are integrally formed. 

1. A pivot mechanism, for the tiltable seat of a chair, comprising a torsion bar, a tube through which said torsion bar extends, the ends of the bar being rigidly secured to the adjacent ends of the tube, means for rigidly securing the tube to the underside of the seat of a chair, a support member in which the central portion of the tube is journaled for rotation about the axis of the tube, the support member having coupling means for mounting the support member on the base of a chair, the tube having an opening in said central portion, an arm rigidly secured to the torsion bar extending outwards through said opening, and a manually operable mechanism for moving the outer end of the arm relative to the support member to vary the torque in the bar.
 2. A mechanism according to claim 1 wherein said support member has bearings for the tube disposed on opposite sides of said opening in the tube.
 3. A pivot mechanism according to claim 2 wherein the base of said chair has an upward extending pedestal, and the coupling means of the support member has a sleeve formed with a tapered seating for the reception therein of a tapered upper end of said pedestal.
 4. A pivot mechanism according to claim 2 having a stop member rigidly secured to the tube for engagement with the support member to limit the pivotal movement of the seat relative to the base of the chair in one direction.
 5. A pivot mechanism for the tiltable seat of a chair, comprising parallel-spaced elongate members for attachment to the seat, a tube extending between and rigidly secured to said elongate members, a torsion bar disposed within the tube and rigidly secured at its ends to the tube and elongate members, a support member disposed adjacent the central portion of the tube and having spaced bearings in which the tube is journaled, and coupling means for securing the support member to a base of the chair, said tube being open between said bearings, and an arm rigidly secured to the torsion bar and extending away from the bar through the opening, the outer end of the arm being movable, relative to an abutment on the support member, by means of a manually operable torque-varying mechanism.
 6. A pivot mechanism according to claim 5 wherein the support member is a casting in which said sleeve, bosses forming said bearings, and said abutment are integrally formed. 